1. Field of the Invention
The present invention relates to a group formation/management system that forms and manages groups within which mutual use of digital contents is possible.
2. Related Art
In recent years, the easy acquisition of digital copyrighted works (hereinafter “contents”), such as music, videos, games and so forth, has become possible as a result of circulation using the Internet, digital broadcast, package media and the like.
Unexamined Japanese patent application no. 2002-169726 discloses a music data management system whose object is to enable use of contents by desiring information processing apparatuses, while preventing use by third parties not having legitimate rights.
In this music data management system, a plurality of personal computers (hereafter “PCs”) each transmit a credit card number or the like to an approved server together with the ID of a computer management program of the PC.
The server receives the ID and the credit card number, and sorts PCs having the same credit card number into the same group. The PCs and their users are registered by recording the IDs and credit card numbers with respect to each group. After registration, the server transmits a group key to each PC together with the ID and password of the corresponding group.
Each PC stores the received group key, group ID and password.
In this way, PCs having the same group key are able to transmit/receive contents using the group key.
With this technology, any device is registerable as an in-group device, and it is possible to freely increase the number of devices registered in any one group.
Furthermore, 5C Digital Transmission Content Protection White Paper (Revision 1.0, Jul. 14, 1998) discloses a specification called digital transmission content protection (DTCP).
DTCP is a protection specification for digital contents delivered via a bus standardized by IEEE 1394, which is a high-speed serial bus standard. Each device that uses contents has a secret key corresponding to the device distributed on the basis of a contract with a manager known as the Digital Transmission Licensing Administrator (DTLA). When contents are to be viewed, mutual authentication is conducted between a transmitting device and a receiving device using the respective secret key, and if authentication is successful, the receiving device is able to view the content.
With this technology, as long as a device receives distribution of a secret key from the DTLA, it is possible, at a time of content usage, for a different device to form a group and use contents.
As such, according to technology disclosed in unexamined Japanese patent application no. 2002-169726 and in 5C Digital Transmission Content Protection White Paper (Revision 1.0, Jul. 14, 1998), it is desirable, from the viewpoint of the copyright protection of material whose content usage is permitted among devices included in a group, to rigidly control the devices forming a group, and from the viewpoint of usability for the user, it is desirable to be able to use contents freely over as wide a scope as possible, using IP (Internet Protocol) for example, rather than only a scope whose transmission range is physically restricted, as is the case with an IEEE 1394 bus.